1. Field of the Invention
The present invention relates generally to medical methods and apparatus. More particularly, the present invention relates to methods and apparatus for the assessment and treatment of lung diseases, such as chronic obstructive pulmonary disease, by detecting the status of the disease and determining an appropriate treatment protocol.
Chronic obstructive pulmonary disease (COPD) is a significant medical problem affecting sixteen million people or about 6% of the U.S. population. Specific diseases in this group include chronic bronchitis, asthmatic bronchitis, and emphysema. While a number of therapeutic interventions are used and have been proposed, none are completely effective, and COPD remains the fourth most common cause of death in the United States. Thus, improved and alternative treatments and therapies would be of significant benefit.
Management of COPD is largely medical and infrequently surgical. Initially, exercise and smoking cessation are encouraged. Medications including bronchodilators and anti-inflammatories are routinely prescribed. Pulmonary rehabilitation has been shown to improve quality of life and sense of well being. Long term oxygen is generally reserved for the more severely affected patients.
Emphysema is a condition of the lung characterized by the abnormal permanent enlargement of the airspaces distal to the terminal bronchiole, accompanied by the destruction of their walls. It is known that emphysema and other pulmonary diseases reduce the ability of part of the lungs to fully expel air during the exhalation phase of the breathing cycle. During breathing, the diseased portion of the lung does not fully recoil due to the diseased lung tissue being less elastic than healthy tissue. Consequently, as the airways normally held open by the elastic pull of the lungs become floppy and the diseased lung tissue exerts a diminished driving force during exhalation, the airways close prematurely resulting in air trapping and hyperinflation.
In addition, hyper-expanded lung tissue occupies more of the pleural space than healthy lung tissue. In most cases, only a part of the lung is diseased while the remaining portion is relatively healthy and therefore still able to efficiently carry out oxygen exchange. By taking up more of the pleural space, the hyper-expanded lung tissue reduces the space available to accommodate the healthy, functioning lung tissue. As a result, the hyper-expanded lung tissue causes inefficient breathing by compressing the adjacent functional airways, alveolar units, and capillaries in relatively healthier lung tissue.
Lung function in patients suffering from some forms of COPD can be improved by reducing the effective lung volume, typically by resecting diseased portions of the lung. Resection of diseased portions of the lungs both promotes expansion of the non-diseased regions of the lung and decreases the portion of inhaled air which goes into the lungs but is unable to transfer oxygen to the blood. Accordingly, recruitment of previously compressed functional airways, alveolar units, and capillaries in relatively healthier lung is possible resulting in more gas exchange in addition to better matching of lung and chest wall dimensions. Lung reduction is conventionally performed in open chest or thoracoscopic procedures where the lung is resected, typically using stapling devices having integral cutting blades.
While effective in many cases, conventional lung volume reduction surgery (LVRS) is significantly traumatic to the patient, even when thoracoscopic procedures are employed. Such procedures often result in the unintentional removal of healthy lung tissue, and frequently leave perforations or other discontinuities in the lung which result in air leakage from the remaining lung. Even technically successful procedures can cause respiratory failure, pneumonia, and death. In addition, many older or compromised patients are not able to be candidates for these procedures.
As an alternative to LVRS, endobronchial volume reduction (EVR) uses endobronchially introduced devices which plug or otherwise isolate a diseased compartment from healthier regions of the lung in order to achieve volume reduction of the diseased compartment. Isolation devices may be implanted in the main airways feeding the diseased region of the lung, and volume reduction takes place via absorption atelectasis after implantation or via collapse by actively suctioning of the target compartment prior to implantation. These implanted isolation devices can be, for example, self-expanding occlusive stents that prevent air flow in both directions or one-way valves that allow flow in the exhalation direction only.
While a significant improvement over LVRS, EVR can have a limited therapeutic benefit when the treated region in the lung is exposed to collateral ventilation from adjacent regions. The lungs comprise a plurality of compartments, referred to as lung compartments or lobes, which are separated from one another by a double layer of enfolded reflections of visceral pleura, referred to as fissures. While the fissures which separate the compartments are typically impermeable, in patients suffering from COPD, the fissures are frequently incomplete, leaving a pathway for collateral airflow or inter-lobular collateral ventilation. Such collateral airflow can result in the intrusion of air into the isolated lung compartments treated by LVR, thus reducing or eliminating the desired volume reduction.
While collateral flow to diseased lung compartments can be detected, for example using the methods described in copending, commonly-owned U.S. patent application Ser. No. 11/296,591, filed on Dec. 7, 2005 (US 2006/0264772A1) and Ser. No. 11/550,660, filed on Oct. 18, 2006 (US 2007/0142742A1). While the use of these procedures can identify patents likely to benefit from EVR procedures, the need to perform a separate diagnostic procedure prior to a therapeutic procedure is time consuming, costly, and inconvenient for the patient.
For these reasons, it would be desirable to provide alternative and improved methods and apparatus for performing endobronchial volume reduction (EVR) and other lung therapies in an efficient and effective manner. In particular, it would be desirable to provide methods and apparatus which permit both the detection of collateral ventilation and subsequent treatment of diseased lung compartments in a single protocol where the treatment is completed only for those patients having no or an acceptable level of collateral ventilation. At least some of these objectives will be met by the inventions described hereinbelow.
2. Description of the Background Art
Exemplary methods for treating diseased lung compartments by isolating the diseased regions are described, for example, in U.S. Pat. Nos. 6,287,290; 6,679,264; 6,722,360; 7,011,094; and printed publication U.S. 2007/0005083. Methods for detecting collateral ventilation prior to treatment of diseased lung regions are described in patent publications U.S. 2006/0264772A1 and U.S. 2007/0142742A1, the full disclosures of which have been previously incorporated herein by reference.